Rongguang Liang

Bio: Rongguang Liang is an academic researcher from University of Arizona. The author has contributed to research in topics: Lens (optics) & Interferometry. The author has an hindex of 29, co-authored 221 publications receiving 3165 citations. Previous affiliations of Rongguang Liang include Carestream Health & Eastman Kodak Company.

Apparatus for caries detection

Abstract: An apparatus for obtaining an image of a tooth having at least one light source providing incident light having a first spectral range for obtaining a reflectance image from the tooth and a second spectral range for exciting a fluorescence image from the tooth. A polarizing beamsplitter in the path of the incident light from both sources directs light having a first polarization state toward the tooth and directs light from the tooth having a second polarization state along a return path toward a sensor, wherein the second polarization state is orthogonal to the first polarization state. A first lens in the return path directs image-bearing light from the tooth toward the sensor, and obtains image data from the portion of the light having the second polarization state. A long-pass filter in the return path attenuates light in the second spectral range.

Real-time Fluorescence Image-Guided Oncologic Surgery

Abstract: Medical imaging plays a critical role in cancer diagnosis and planning. Many of these patients rely on surgical intervention for curative outcomes. This requires a careful identification of the primary and microscopic tumors, and the complete removal of cancer. Although there have been efforts to adapt traditional-imaging modalities for intraoperative image guidance, they suffer from several constraints such as large hardware footprint, high-operation cost, and disruption of the surgical workflow. Because of the ease of image acquisition, relatively low-cost devices and intuitive operation, optical imaging methods have received tremendous interests for use in real-time image-guided surgery. To improve imaging depth under low interference by tissue autofluorescence, many of these applications utilize light in the near-infrared (NIR) wavelengths, which is invisible to human eyes. With the availability of a wide selection of tumor-avid contrast agents, advancements in imaging sensors, electronic and optical designs, surgeons are able to combine different attributes of NIR optical imaging techniques to improve treatment outcomes. The emergence of diverse commercial and experimental image guidance systems, which are in various stages of clinical translation, attests to the potential high impact of intraoperative optical imaging methods to improve speed of oncologic surgery with high accuracy and minimal margin positivity.

Multi-polarization fringe projection imaging for high dynamic range objects.

Abstract: Traditional fringe-projection three-dimensional (3D) imaging techniques struggle to estimate the shape of high dynamic range (HDR) objects where detected fringes are of limited visibility. Moreover, saturated regions of specular reflections can completely block any fringe patterns, leading to lost depth information. We propose a multi-polarization fringe projection (MPFP) imaging technique that eliminates saturated points and enhances the fringe contrast by selecting the proper polarized channel measurements. The developed technique can be easily extended to include measurements captured under different exposure times to obtain more accurate shape rendering for very HDR objects.

Design of Freeform Illumination Optics

Abstract: Freeform optics constitutes a new technology that is currently driving substantial changes in illumination design. It liberates designers and engineers from restrictions of optical surface geometry, enabling them to achieve compact, lightweight, and efficient illumination systems with excellent optical performance. Freeform optics is currently used widely for both fundamental research and practical applications. This Review focuses on the design of freeform illumination optics, which is a key factor in advancing the development of illumination engineering. The design methods of freeform illumination optics can be divided into two groups: zero-´etendue algorithms based on ideal source assumption and design algorithms for extended light sources. The zero-´etendue algorithms include ray mapping method, Monge–Ampere equation method, and supporting quadric method. The algorithms for extended sources include illumination optimization, feedback design, and simultaneous multiple surfaces method. The characteristics and limitations of these design methods are illustrated and a summary of these methods with future outlooks is also given.

Intra-oral camera for diagnostic and cosmetic imaging

Abstract: An apparatus for obtaining images of a tooth comprises at least one image sensor disposed along an optical axis to take polarized reflectance image and fluorescence image, at least one broadband illumination apparatus for reflectance imaging, and a narrow-band ultraviolet illumination apparatus for fluorescence imaging. In order to remove the specular reflection, one or more polarization elements are disposed along the optical axis. A filter is disposed along the optical axis to block narrow-band ultraviolet light, and a switch for selecting one of the operation modes.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

Abstract: A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Virtual and augmented reality systems and methods

Abstract: Methods of manufacturing a liquid crystal device including depositing a layer of liquid crystal material on a substrate and imprinting a pattern on the layer of liquid crystal material using an imprint template are disclosed. The liquid crystal material can be jet deposited. The imprint template can include surface relief features, Pancharatnam-Berry Phase Effect (PBPE) structures or diffractive structures. The liquid crystal device manufactured by the methods described herein can be used to manipulate light, such as for beam steering, wavefront shaping, separating wavelengths and/or polarizations, and combining different wavelengths and/or polarizations.